Warp let-off motion



Filed April 13, 1967 Sheet Feb 1969 E. PFARRWALLER 3,426,805

WARP LET -OFF MOTION Fig. 1

Inventor.- Erwin Pforr wuller AT TOR N EYS Feb. 11, 1969 E. F'FARRWALLER 3,426,806

WARP LET-OFF MOTION Filed April 13, 1967 Sheet 2 of 5 Inventor- Erwin Pforrwcller BYGW'M MJ M16 4.

A TORNEYS Feb. 11, 1969 E. PFARRWALLER 3,426,806

WARP LET-OFF MOTION Filed April 13, 1967 Sheet 3 of 5 Inventor.- Erwin Pforrwuller M14 4 M1 G4,.

ATTORNEYS United States Patent 5,341/ 66 US. Cl. 139-101 6 Claims Int. Cl. D03d 49/06, 48/10; D04b 27/12 ABSTRACT OF THE DISCLOSURE There is disclosed a warp let-off motion for the let-off of warp threads from a plurality of warp beams which may have equal or unequal numbers of threads thereon, the let-oft" maintaining as desired either equal or unequal tensions in the warps from the individual beams. The let-off motion includes a differential gear train. The let-off motion proper is applied through a non-reversing worm and worm gear to the cage of this differential and each of the beams is coupled directly or indirectly to one of the other driving points of the differential. A transmission, in the form of gears or sprockets for example, having a non-unity drive ratio between its two ends, is connected between one of the beams and the addition of motions in the differential, this transmission being thus either inside or outside the differential. By means of this non-unity drive ratio, equilibrium in the differential may be established for unlike torques at two of the warp beams. Plural such arrangements may be provided to permit maintenance of two different torques among three or more beams.

BACKGROUND OF THE INVENTION Field of the invention In the operation of looms having two or more warp beams it has been heretofore proposed, for avoidance of unlike tension among the various warp threads in the cloth, to equalize with the help of a differential gear train the torques exerted on those beams by the warp threads which are stretched therefrom. This differential is coupled to the drive of the loom or of the cloth beam by means of a transmission which is adjusted in accordance with the stress exerted by the warp threads or by the cloth on a tension beam of the loom. In this way, the separate warp beams are permitted to rotate in accordance with the pull-off of the cloth so as to permit delivery of the necessary lengths of warp thread at constant tension. The tension exerted on the warp threads by the tension beam develops a total tension or torque which is uniformly distributed among the two warp beams by operation of the differential.

In another warp let-off motion heretofore proposed,

Patented Feb. 11, 1969 a brake is combined with the differential gear train. There is thus developed a braking torque or moment which is uniformly distributed between the two warp beams and which opposes the torques exerted thereon by the warp threads. For let-off or delivery of warp thread the brake is released or partially released, so that the warp beams are set in motion under influence of the cloth beam drive, and in this way the necessary predetermined length of warp thread is delivered.

The warp let-oil mot-ions heretofore proposed are welladapted for the operation of looms having plural warp beams in which the warp threads are wound to the same thickness or diameter on both beams and in which the two beams are of equal width, carrying equal numbers r of warp threads. In general, the warp threads drawn off of any one warp beam serve for the production of a single separate web of cloth.

According to the nature of the cloth to be woven, and to the nature of the warp beams available, it may be necessary to weave three separate widths of cloth on a loom having two warp beams. If the warp beams are of the same width then the middle web of cloth must be woven half from each of the two warp beams. The result is that defects in weaving can occur at the junction point where the warp threads from the two beams adjoin each other, these defects being a result of variation in friction within the differential upon action thereof to equalize the tensions exerted by the two sets of warp threads. For this reason, it is advantageous to employ two warp beams of unlike width. The warp threads withdrawn from the longer or wider beam serve for the production of two complete cloth webs whereas those withdrawn from the other beam serve for the production of a single width of cloth.

Relatively large and troublesome variations or differences in tension can however arise as between the webs of cloth being woven with looms of this type in which the warp beams carry unlike numbers of warp threads and which employ known warp let-off motions. The equal pul-l-ofr" torques distributed to the warp beams produce equal aggregate pull-oft stresses on the two warp beams despite their unlike width. Since these stresses are the resultant of the tensions in the individual warp threads, the tension of the individual warp threads is less in those which come from the beam of greater width than in those which come from the beam of lesser width. Differences in tension of this type between Webs being simultaneously woven on a loom are in general undesirable.

Summary of the invention It is an object of the invention to surmount this difficulty and to provide apparatus by means of which there is maintained among all warp threads coming from two separate beams either the same tension or a specified predetermined difference in tension, the tension being held for each of the warp beams at a specified value.

In accordance with the invention, the warp let-off motion is so constructed that the mechanical coupling between the warp beams produces unlike torques on them.

According to one embodiment of the invention, the drive ratio of the (typically non-unity) drive or transmission by which one beam is coupled to another is made to be substantially proportional to the ratio of the widths of those beams. In this way, the troques exerted on the beams by the tension of the warp threads may be distributed among the beams in correspondence with the unlike numbers of warp threads thereon so as to subject each of the warp threads to the same tension. This is particularly advantageous when plural webs of cloth of unlike widths are to be simultaneously woven.

In one embodiment of the invention the coupling or linkagetypically a gear train or a portion of a gear train-which exhibits the drive ratio of other than unity value by which the unequal warp beam troques are produced, is disposed between two of the three drive points of a differential gearing, each of these two points being coupled via suitable linkage or gearing to a separate one of the warp beams. This constitutes a particularly simple and economic embodiment of the invention, well-adapted for a loom drive in which a given torque radio among the plural warp beams once chosen is to be preserved. In the event of a change in the necessary torque ratio the whole differential can readily be withdrawn and replaced with another.

To clarify the notion of the drive points of a differential, it may be pointed out that a differential is an epicyclic gear train in which rotations can be applied independently to two points to produce at a third point a rotation which is the algebraic sum of the rotations applied to the first two points. All three of these points may be referred to as the drive points of the differential, although the differential may be so constructed that one of these points can function as an input point only, being incapable of delivering motion applied to either or both of the other points.

According to another embodiment of the invention, the elements possessing the non-unity drive ratio are disposed in a drive train extending between one of the warp beams and one of the drive points of the differential. In this way, therefore, the differential customarily provided for equalization of small differences in rotation is supplemented by a further and non-unity ratio drive, for example a gear train or a chain drive or a continuously variable ratio drive. This last is particularly adapted for use on a loom in which cloth webs of various and changing widths are to be woven, the ratio of the non-unity ratio drive being quickly and simply adjusted according to circumstances. The differential drive of previously proposed warp let-off motions can moreover be simply and economically supplemented with the non-unity ratio drive of the invention.

The drive ratio between the two driving points of the non-unity ratio drive can be chosen anywhere within a relatively wide range. For example, it may be desired to make this ratio only approximately rather than exactly proportional to the ratio of the torques. This can, for example, be the case when unequal frictional resistances are experienced within the separate warp beam drives, so as to permit simple correction and compensation therefor by slight shift in the drive ratio.

A drive of the type provided by the invention can be employed to couple together warp beams superposed one above the other. Warp beams so disposed make it possible to double the operating time between necessary changes of empty warp beams, if the warp threads required for unit width in the finished cloth are to come from two parallel beams of the same width instead of from one beam. By means of the invention moreover, unlike tension may be applied to and maintained in the two sets of warp threads coming from the two beams. This is advantageous for example in the weaving of terry cloth, rugs and the like having plural unlike sets of warp threads.

In one embodiment of the invention having plural Warp beams coupled together by two differentials, the non-unity drive ratio is included in a transmission connected between two points each coupled with a drive point in a separate one of the two differentials. In this way, it is possible positively to couple together two warp beams, for example, disposed one above the other, and

employed for the weaving of separate cloth webs. The drive ratio can be selected anywhere within a wide range of values.

Brief description of the drawings The invention will now be further described in terms of a number of exemplary embodiments and with reference to the accompanying drawings, wherein:

FIG. 1 is a view in rear elevation, i.e. from the warp end, and partly in section, of a loom according to the invention;

FIG. 2 is a sectional view taken on the line IIII of FIG. 1 but shown at an enlarged scale;

FIG. 3 is a view similar to that of FIG. 1 but showing a modified embodiment of the invention;

FIG. 4 is a sectional view taken on the line IV--IV of FIG. 3 but shown at an enlarged scale;

FIG. 5 is a further view similar to that of FIG. 1 but showing still another embodiment of the invention;

FIG. 6 is a diagrammatic view in side elevation of the apparatus of FIG. 5 taken in the direction indicated by the arrow of VI in FIG. 5; and

FIG. 7 is still another view similar to that of FIG. 5 but showing still another embodiment of the invention.

There is shown schematically in FIG. 1 a gripper shuttle loom having side members 1 and 2 between which is disposed a warp thread supply comprising separate warp beams 3 and 4. The loom also includes a tensioning beam 5. The shaft 6 of the tension beam 5 is supported in bearings, not shown, disposed in the side members 1 and 2. The warp beams 3 and 4 comprise each a shaft 7, a warp beam tube 8, and two flanges 9 and 10. The shafts 7 are supported each in a separate bearing in one of side members 1 and 2 and additionally in a central bearing 13 supported on a rest or pillar 34.

The warp beam flanges 9 and 10 define the widths of the separate warp beams 3 and 4 on which warp threads 11 and 12 are wound up. In the loom of FIG. 1, the width of the warp beam 4 is twice that of the warp beam 3.

The warp threads 11 and 12 pass from the beams 3 and 4 over the tension beam 5. In a manner similar to that shown for the warp threads 93 in the loom of FIG. 6, the warp threads 11 and 12 of FIG. 1 pass over guide rollers as shown at 42 in FIG. 6 and through shedding harnesses 43 and 44 which serve for the formation of a shed indicated at 45 in FIG. 6. Between the guide rollers 42 thread monitoring devices 41 are provided which develop a signal in the event of warp thread breakage so as to discontinue operation of the loom. A weft thread is inserted into the shed 45 by picking mechanism which may be conventional, not shown in either FIG. 1 or FIG. 6. More particularly, the weft thread is inserted by means of a gripper shuttle 46. The shuttle is shot through the shed from a picking mechanism, also not shown, disposed on the side column 2 in FIG. 1, to a catching mechanism, likewise not shown, and disposed on the side member 1.

The weft thread is beaten up into the cloth at the fell 45' of the cloth by means of a reed 47 (FIG. 6). After change of shed, a new pick occurs. The cloth 48 so woven passes through temples 49 and over a breast beam 50 to a take-up beam 51 and finally over a direction changing roller 52 to a cloth beam 53 on which the finished cloth is wound up.

Returning to FIG. 1, the warp beams 3 and 4 are provided each with a separate drive. The beam 3 has fastened thereto a gear 14 which meshes with a pinion 16 fixed on a shaft 15. In similar fashion, the beam 4 has affixed thereto a gear 17 which meshes with a pinion 18. The gears 14 and 17 have the same number of teeth, and so do the pinions 16 and 18. The pinion 18 is fast to a hollow shaft 19 rotatably supported in a bearing 20 of the side column 2. The shaft 15 is rotatably supported in a bearing, not shown, disposed in the side member 1 and is additionally supported in the hollow shaft 19 for rotation with respect thereto. The two shafts and 19 pass through the side member 2 into the housing 22 of a differential drive 21, the housing 22 being on the exterior of the side member 2. Within the housing 22 is disposed a gear 23 fast on the shaft 15 while the hollow shaft 19 has fastened thereto a gear 24.

The gear 24 meshes with two planetary gears 25 (FIG. 2). These planetary gears are affixed each to a separate further planetary gear 26 (having a larger number of teeth) coaxial therewith, each pair of coaxial gears being mounted on a shaft 27 journaled in housing 22. The planetary gears 26 mesh with separate planetary gears 28 of smaller tooth number. The planetary gears 28 are fixed each coaxially to a further planetary gear 29 of larger tooth number and are supported on separate shafts 30 also journaled in housing 22. The two planetary gears 29 mesh with the gear 23, fast on shaft 15.

The housing or cage 22 of the differential gear train 21 is rotatably supported on the hollow shaft 19 and on the shaft 15. A worm wheel 31 fixed on the housing 22 meshes with a worm 32 fast on a shaft 33. The Worm wheel 31 and the gears 23 and 24 constitute the three drive points of the differential 21. The numbers of teeth on the gears within the housing are so chosen that a drive ratio of 2:1 exists between the gears 24 and 23, i.e. between the shafts 15 and 19, assuming the housing 22 to be stationary. That is to say, with the housing stationary, one revolution of gear 24 will produce two revolutions of gear 23.

The mode of operation of the loom of FIG. 1 is as follows:

The warp threads 11 and 12 are subjected to tension by operation of the tension beam 5 and of a drive (not shown) to the worm 32 dependent on the stress exerted on the tension beam by the threads 11 and 12, and this tension is maintained constant so that the total tension or pull-off stress in the threads 11 and 12 is maintained substantially constant, independent of changes in the diameter of the mass of warp thread on the beams. For brevity, this diameter will hereinafter be referred to simply as the diameter of the warp beam or beams.

The warp threads 11 and 12 thus exert torques on the beams 3 and 4. These torques are transferred to the housing 22 of the differential drive 21 by means of the gears 23 and 24 and thence via the planetary gears 29, 28 and 25, 26, both of the gears 26 and 28 suffering counterclockwise torque as seen in FIG. 2. The housing 22 is driven by the worm wheel 31 by operation of the worm 32. The shaft 33 of the worm is coupled, by means of a control drive (not shown) variable in accordance with the position of the tension beam 5, to the loom drive itself, likewise not shown. The worm 32 is self-blocking, i.e. so constructed it will not drive backwardly, so that when the beams 3 and 4 are stationary, the housing 22 is prevented from rotating under influence of the torque experienced by the beams 3 and 4. That is, the worm and worm wheel constitute a one-way drive. In this way, the counter-torque necessary for maintenance of the weft thread tensions is preserved.

The pull-off forces exerted by the weft threads 11 and 12 are distributed between the beams 3 and 4 by the differential gear train 21. In view of the dimensions of the gears 24 and 23 and of the planetary gears 25, 26, 28 and 29, the torque transmitted by the gear 24 is twice as great as the torque on the gear 23. By virtue of the equality to each other of the warp beam gear trains 16, 14 and 18, 17, therefore, there will be exerted on the beam 4 a torque twice as great as that exerted on the beam 3 so that there will be exerted on the threads 12 an aggregate pull-off stress twice as great as that exerted on the threads 11.

Since the width of the beam 4 and hence the number of threads 12 thereon are respectively twice as great as the width and number of warp threads on the beam 3, all of the threads 11 and 12 experience the same tension.

For let-off of the threads 11 and 12, the housing 22 is rotated by the worm 32 to an extent such that the necessary length of warp thread can be drawn of1 of the beams 3 and 4. The beams 3 and 4 rotate through the same angle and the torques exerted in them preserve a constant ratio.

During normal operation of the loom and with equal thread diameters on the beams 3 and 4, the housing 22 and the gears 23 and 24 rotate in the same direction and through the same angles. The planetary gears 25, 26, 28 and 29 do not rotate about their shafts 27 and 30 but rather function simply as couplings between the housing 22 and the gears 23 and 24.

In the event of irregularities in the laying of the warp threads onto the beams 3 and 4, and particularly in the event of the occurrence of unlike frictional resistances in the bearings of the beams 3 and 4, the angles through which those beams rotate may differ. Small variations of this kind encountered in practice are compensated out by the differential gear train 21. Upon an increase in the rotation of beam 4, for example, and consequently of the gear 24, the planetary gears 25, 26 and 28, 29 will in known fashion rotate on their shafts '27 and 30, the rotation of the housing 22 continuing unchanged. In this way, the tension of the weft thread groups 11 and 12 and consequently the pull-off torques on the beams 3 and 4 will be maintained constant during the operation.

The loom according to FIG. 3 includes elements I to 13, 16 to 20, 24, 32 and 34 (and also 41 to 53 as illustrated in FIG. 6) which are the same as the correspondingly identified elements of structure in the loom of FIG. 1, and is constructed in generally the same way as the loom of FIG. 1. The pinion 16 of the drive to beam 3 is fastened to a shaft 60 which is rotatably supported by an end bearing, not shown, disposed in the side support 1 and in the hollow shaft 19. The shaft 69 passes out through the hollow shaft 19 and into and through housing 62 disposed on the exterior side of the side support 2, this housing 62 being that of a differential gear train 61. On its end beyond housing 62 the shaft 60 carries a gear 63.

A gear 24 fastened to the hollow shaft '19 meshes inside the housing 62 with two planetary gears '64 (see FIG. 4). These gears are supported on shafts 65 journaled in the housing 62. The gears 64 mesh with two planetary gears 66 On shafts 67, also journaled in the housing 62. The gears 66 mesh with a gear 68 fast on a hollow shaft 69 freely supported on the shaft 60. The hollow shaft 69 passes out through the housing 62 and carries on the exterior thereof a gear 70 which is in mesh with a gear 71.

The gear 71 is fastened to a shaft 72 which is borne in stationary bearings 73 and which carries a further gear 74 affixed thereto. The bearings 73 are disposed in an arm 75 afiixed to the side member 2. The gear 74 meshes with the gear 63. Gears 70, 71, 74 and 63 constitute a spur gear train in which gears 74 and 63 serve for speed change purposes.

The housing 62 of the differential '61 is rotatably sup ported on hollow shaft-s 19 and 69 (the latter, in turn, being rotatably supported on shaft 60). Housing 62 has affixed thereto a worm wheel 76 which is in mesh with a worm 32 on a shaft 33. Worm wheel 76, gear 24 (i.e. shaft 19) and gear 68 (i.e. shaft 69) constitute the drive points of the differential 61. The gears 24 and 68 have the same number of teeth and so do all four of the gears 64 and 66. For this reason the drive ratio between the gears 24 and 68 is 1:1, and so also is the drive ratio between the shafts 19 and 69. The gears 70, 71, 74 and 63 are chosen to provide a speed ratio of 2:1 between the hollow shaft 69 and the shaft 60.

The mode of operation of the embodiment of FIGS. 3 and 4 is as follows: The torques applied to the beams 3 and 4 by the threads 11 and 12 are transmitted by their drives to the gears 63 and 24 respectively. The torque of the gear 24 is transmitted through the planetary gears 64 and their shafts 65 to housing 62 of the differential 6 1.

The torque of gear 63 instead passes through the gear train 70-74 and to the gear 68 and thence via the planetary gears 66 and their shafts 67 to the housing 62.

The housing 62 is, as in the loom of FIG. 1, driven by a non-reverse driving worm 32 and is hence prevented from rotation except by rotation applied to the worm 32.

The pull-off stress of the threads 11 and 12 is distributed between the beams 3 and 4 by the differential 61. In known fashion, equal torques are transmitted by the gears 24 and 68. The torque on the gear 68 is, however, twice as great as that on the gear 63 in view of the 2:1 drive ratio already mentioned for the gears 70, 71, 74 and 63. The result is that the beam 4 is subjected to a torque twice as great as that as the beam 3. The two groups 11 and 12 of warp threads are therefore subjected to the same tension, assuming twice as many threads 12 as threads 11.

For let-off of the warp threads 11 and 12 the housing 62 is rotated by the worm 32 in a fashion similar to that in which the housing 22 is rotated in FIG. '1. Since the two beams 3 and 4 deliver the same length of warp threads, the gears 24 and 63 rotate through the same angles. Correspondingly, in view of the 2:1 drive ratio of the gears 74 and 63, the gear 68 rotates through half the angular distance traversed by the gear 24 so that the rotation of the housing 61 must be appropriately chosen, in known fashion. During this rotation of the differential housing 62, the planetary gears 64 and 66 rotate with their shafts 65 and 67 and roll on the gears '68 and 24. Variations in resistance to pull-off which may be experienced in operation are compensated out in known fashion by operation of the differential 61.

In the gripper shuttle loom of FIGS. and 6 two warp beams 83 and 84 are disposed one above another between the side members 81 and 82 of the loom. The beams 83 and 84 comprise each a shaft 85, a tube 86 and two flanges 87 and 88 which can be fixed at any desired points along the tubes. The beams 83 and 84 and their shafts 85 are supported for rotation in bearings, not shown, in the side members 81 and 82. Two tension beams 89 and 90 are disposed one above another between the beams 83 and 84, the shafts 91 of the beams 89 and 90 being rotatably supported in bearings, not shown, in the loom frame members 81 and 82.

The flanges 87 and 88 define equal widths on the beams 83 and 84, within which the warp threads are wound. Both of the beams 83 and 84 carry the same number of warp threads 92 and 93 of the same length and thickness so that the ratio of the diameters of the two beams is substantially constant and substantially equal to unity. The upper warp threads 92 are subjected to a smaller tension than the lower warp threads 93.

The threads 92 pass from the upper beam 83 under the upper tension beam 89 while the threads 93 pass from the lower beam 84 over the lower tension beam 90. The threads 92 and 93 pass together from the tension beams 89 and 90 over two guide rolls 42 (FIG. 6) into the harnesses 43 and 44 and thence pass in known fashion into the cloth 48 and to the cloth beam 53.

The warp beams 83 and 84 are provided with separate drives. The beam 83 is ifixed to a gear 94 which meshes with a pinion 95 in mesh in turn with a pinion 96. The pinion 95 is rotatably supported on a stub shaft 80 in the side member 82. The pinion 96 is fixed on a shaft 97 which is rotatably supported in a bearing 98 in the side member 82, and also in a bearing 99 of an arm 100 affixed to the side member 82. The shaft 97 passes the bearing 99 and carries a sprocket 101 on its free end.

The beam 84 is affixed to a gear 102 which meshes with a pinion 103. The gears 94 and 102 have the same number of teeth and the pinions 96 and 103 also have the same number of teeth. Pinion 103 is fixed to a hollow shaft 104 which is borne in a bearing 105 in side member 82. Shaft 104 passes through the side member into a housing 107 of a differential gear train 106 on the ex- 8 terior of the side member 82. Within the housing 107 hollow shaft 104 has affixed thereto a gear 108. A gear 110 is fastened, inside the housing 107, to a shaft 109 rotatably supported in the hollow shaft 104 and in housing 107. A sprocket wheel 111 outside the housing 107 is additionally affixed to the shaft 109.

The gear 108 meshes with two planetary gears 112 (FIG. 6). These planetary gears are supported on shafts 113 journalled in the housing 107 and mesh with planetary gears 114 supported on shafts 115, also jour-naled in the housing 107. The planetary gears 114 also mesh with the gear 110.

The housing 107 is rotatably supported on the hollow shaft 104 and also on the shaft 109 and carries a worm wheel 116 which meshes with a worm 118 fastened to a shaft 117. The worm 117 and the gears 108 and 110 constitute the drive points of the differential drive 106. The gears 108 and 110 have the same number of teeth, as do all four of the planetary gears 112 and 114. For this reason there exists between the gears 108 and 110, and hence between the hollow shaft 104 and the shaft 109, a drive ratio of 1:1

The sprocket wheels 101 and 111 are coupled together by means of an endless drive chain 119. A crank arm 121 is adjustably fixable on a stub shaft 120 on the side member 82. This arm 121 carries a shaft 122. A sprocket wheel 123 is rotatably supported on this arm, this sprocket wheel being engageable with the drive chain 119 to hold it taut. The sprocket wheels 101 and 111 can be removed from their respective shafts 97 and 109 and replaced with others of different numbers of teeth, so that they can be regarded as the end points of a coupling or transfer drive. The sprocket wheel 101 is smaller than the sprocket wheel 111. The diameters and tooth numbers are so chosen as to provide between the shafts 109 and 97 a drive ratio corresponding to the desired ratio between the torques to be established in the warp beams 83 and 84 by pull thereon of the warp threads 92 and 93.

The apparatus of FIG. 5 operates as follows: By means of a variable drive (not shown) to the worm 118 which responds to the stresses imposed by the warp threads on the tension beams 89 and and which may originate at the main loom drive, there is established and maintained a tension in the warp threads 92 and 93 such that the total pull-off force of the warp threads 92 and 93 remains substantially constant irrespective of changes in the eifective diameter of the warp beams 83 and 84.

The warp threads 92 and 93 exert torques on the warp beams 83 and 84 which are transmitted by the respective warp beam drives to the sprocket wheel 101 (for beam 83) and to the gear 108 (for beam 84). The torque imposed on the gear 108 is transmitted through the planetary gears 112 and shafts 113 to the housing 107 of the differential 106. The torque imposed on the sprocket wheel 101 is transmitted by the drive sprocket chain 119 to the sprocket wheel 111, to the gear and thence via the planetary gears 114 and shafts to the housing 107. The housing 107 is driven by the worm 118 through the worm wheel 116. The shaft 117 of the worm 118 is coupled to the drive already mentioned, originating at the main loom drive and which is modified by the position assumed by the tension beams 89 and 91 in response to the stress exerted thereon by the warp threads. The worm 118 is not reversible so that when the warp beams 83, 84 are at rest, the housing 107 is prevented from moving in response to the torque experienced by those warp beams. Consequently, the torque necessary to proper tensioning of the warp threads is maintained.

The pull-off tension in the warp threads 92 and 93 is distributed between the beams 83 and 84 by the differential drive 106. Equal torques are transmitted by the gears 108 and 110 in view of the relative tooth numbers of those gears and of the planetary gears 112 and 114 already described. The torque in the gear 110 is however larger than that in the sprocket 101, corresponding to the drive ratio between the sprocket wheels 111 and 101. Consequently, there is applied to the beam 84 a larger torque than to the beam 83. Since the warp beams 83 and 84 have the same width, the warp threads 93 are subjected to larger tension than are the threads 92. Otherwise stated, with sprocket wheel 101' smaller than sprocket wheel 111, the torque to which the upper beam 83 is subjected is smaller than that to which the lower beam is subjected. Hence if both beams carry the same number of threads at the same radius, the tension will be less in the upper warp threads 92 than in the lower Warp threads 93.

For let-off of the threads 92 and 93, the differential housing or cage 107 is rotated by the worm 118 to an extent such that the necessary thread length can be pulled off of the warp beams 83 and 84. In normal loom operation, it is in general desired to have a constant length of warp thread pulled off of the beams in unit time. This means, for equal diameters of the quantities of thread on the two beams, equal rotations of the beams 83 and 84 and hence of the gear 108 and sprocket 101. This in turn means, in view of the non-unity transmission ratio between sprockets 101 and 111, that the gear 110 will then execute a smaller rotation than the gear 108. This determines, according to the classical properties of a differential gear train, the necessary rotation of the housing 107. The planetary gears 112 and 114 rotate with their shafts 113 and 115 and roll upon and in mesh with the gears 108 and 110. Any irregularities occurring in the let-off of the two sets of Warp threads are compensated out in known fashion by the operation of the differential 106.

If desired, the warp beams 83 and 84 may support unequal numbers of warp threads 92' and 93. For example, the upper warp beam 83 may have by comparison with the warp beam "84 a smaller width, specified by flanges 87 and 88, so that the number of warp threads 92' on the upper beam is smaller than the number of Warp threads 93 on the lower beam. By operation of the differential 106 and of the sprocket drive 101, I19, 111 there will then be exerted on the warp beam 83, as before, a smaller pull-off torque than on the beam 84. For a transmission or drive ratio of the sprocket Wheels 101 and 111 corresponding to the unlike distribution of warp threads 92' and 93, i.e. corresponding to ratio of 'the widths of the warp beams between their flanges, it is possible to obtain equal tensions in the warp threads 92' and 93, for a constant relation of the diameters of the quantities of thread on those warp beams.

The loom according to FIG. 7 includes elements 80, 84 to 91, 95 and 102 to 123 which may be the same as the correspondingly numbered elements in the loom of FIG. '5. A warp beam '84, two tension beams 89 and 90 and two half warp beams 133 and 134 are disposed be tween side members 131 and 132. The half beams 133 and 134 comprise each a warp beam shaft 135, a warp beam tube 136 thereon, and two flanges 137 and .138 which are adjustably fixable on the tube 136. The half beams 133 and 134 are rotatably borne together with the shafts 1 35 in bearings not shown but provided in the side members 13 1 and 132 and additionally in a central bearing 140 supported on a pillar 139'.

The warp beam flanges 87 and 8 8 and the two pairs of flanges 137 and 138 define on the warp beam 84 and on the half warp beams 133 and 134 appropriate warp beam widths for the warp threads 141 for the beam 87 and 142 and 143 for the warp beams 133 and 134. These threads may all be of the same length and thickness. The two half beams 133 and 134 are of the same width and carry the same number of warp threads 142 and 143. The number of warp threads distributed over the lower beam 84 is larger than the sum of the warp threads supported on the two half beams 142 and 143. The three beams 133, 13 4 and '84 have the same effective diameters for the masses of threads wound thereon.

The threads 142 and 143 pass from the beams 133 and 134 under an upper tension beam 89 while the threads 141 pass from the lower beam 84 over the lower tension beam 90. The subsequent paths of the warp threads correspond to that of the warp threads 92 and 93 in FIG. 6'. Each of the half beams 133 and 134 is provided with a warp beam drive. The beam 133 is fixed to a gear 144 which meshes via a pinion with a pinion T46 fixed on a shaft 145. Similarly the beam 134 is fixed to a gear 147 which meshes with a pinion 95 which in turn meshes with a pinion 148. The gears 144 and 147 have the same number of teeth and so do the gears 1'46 and '148.

The pinion 148 is fixed on a hollow shaft 149 which is rotatably supported in bearings 150 in the side member 132. The shaft 145 is rotatably supported in a bearing, not shown, provided in the side member 131 and it is also rotatably supported in the hollow shaft 1'49, and with the shaft 149 it passes through the side member 132 into a housing 152 exterior of the side member, this being the housing of a differential gear train 151. Within the housing 152 is provided a gear 153 fixed on the shaft 145. The hollow shaft 149 has affixed thereto a gear 154.

The gear 154 meshes with two planetary gears 155. These are disposed on shafts 1'56 journaled in the housing 152. The planetary gears 155 mesh with two further planetary gears 1'57 supported on shafts 158 journaled in housing 152. The planetary gears 157 mesh with the gear 153. In FIG. 7 only one gear 155 and one gear 1'57 are visible.

The housing 152 is rotatably supported on the hollow shaft 149 and on the shaft 145 and it has aifixed thereto a sprocket wheel 159. This sprocket is coupled by a chain 119 with a sprocket wheel 11-1. The housing-i1 52 and the gears 153 and 154 constitute the drive points of the differential drive 1'51. The gears 153 and 1 54 have the same number of teeth and so have all four of the planetary gears 155 and 157. Between the gears 1'53 and 154 and hence between the shafts 145 and 149 there exists a 1:1 drive ratio, assuming the cage 152 of the differential to be stationary.

The sprocket wheel 159 is removable from the housing 152 so as to be replaceable with another one of different size. The two sprockets 159 and 111 constitute the drive points of a transmission. The sprocket wheel 159 is smaller than the sprocket wheel 1'11. 'Iheir diameters or tooth numbers are so chosen as to provide between the shafts 109 and the housing 152 a drive ratio corresponding to the ratio of the width of beam '84 to the sum of the widths of beams 133 and 1-34.

The mode of operation of this embodiment is as follows: Torques are exerted by the warp threads 141 and 142 and 143 on the beams 84, 133 and 134. These torques are transmitted by the warp beam drives, to the gear 108 as to the beam 84 and to the gears 153 and 154 in the case of the half beams 1 33 and 134. These torques are thence transmitted in turn in known fashion via the planetary gears of their respective differentials, to the housing 152 of differential 151 for the torques of beams 13% and 134 and to the housing 107 of differential 106 for the torque of beam 84. The torque experienced by the housing 152 is transmitted by the sprocket wheel 1'59 and the chain 119 to the sprocket 1'11 and thence to the housing 107 of differential 106 via gear 110 and the planetary gears 114 in mesh therewith.

The housing 107 of the differential 106 is driven as in the loom of FIG. 5 and when the beams 84, 133 and '134 are stationary it is prevented by the one-Way nature of the worm drive 116, 118 from driving backwardly under influence of the torques experienced by the beam 84 and the housing 152.

The pull-off tension of the warp threads 1'41, 142 and 143 is distributed between the lower beam 84 and the upper half beams 133 and 134 by operation of the differential gear train 106. The pull-off tension experienced 1 1 by the warp threads 1 12 and 143 is adjusted by the differential gear train 151.

In correspondence with the drive ratio between the sprocket wheels 111 and 159, the torques imposed on the gears 110 and 108 is larger than that experienced by the housing 152. The torque operating on the beam 84 is consequently larger than the aggregate torque which is equally divided by the differential drive 151 between the two half beams 133 and 134.

'If the drive ratio of the sprocket drive 111, 159 corresponds to the ratio of the width of the beam 84 to the sum of the widths of the beams 133 and 134 and consequently to the ratio of the number of threads 141 to the sum of the numbers of threads 142 and 143, all three sets of warp threads will be subjected to the same tension. The apparatus of FIG. 7 may be employed for the simultaneous weaving of two cloth webs of the same width, the warp threads 142 and 143 having for example different colors and colors different from those of the warp threads 141.

Let-off of the warp threads 141, 142 and 143 is effected in a manner similar to that described in respect of the embodiment of FIG. 5. During normal operation and for a constant ratio of the effective diameters of the warp beams, the beams 133 and 134 execute the same rotations as the housing 152. The planetary gears 155 and 157 are stationary, that is to say, they do not rotate about their own axes and serve only to couple the housing 152 to the gears 153, 154. Irregularities occurring between the half beams 133 and 134 are compensated in known fashion in that the planetary gears 155 and 157 execute small rotations with their shafts 156 and 158 and roll over the gears 153 and 154. Thus, even with unequal rotations of the half beams 133 and 134, there will be effected a uniform or equal distribution of pull-off torques and hence a constant tension will be maintained in the warp threads.

According to a further embodiment of the invention the half beams may be of unequal lengths, for example, for the weaving of three webs. In place of the differential 151, there can be employed other apparatus which may for example be similar to that of the differential drive 21 as shown in FIG. 1, provided however, with a sprocket drive. In place of a sprocket drive it is also possible to employ gears or other variable ratio drive apparatus.

With respect to the several exemplary, non-limitative examples of the invention which have been described hereinabove, it may be noted that in that of FIG. 1 a torque load on gear 23 (i.e. on beam 3) one half that on gear 24 (i.e. on beam 4) can be sustained without differential action (i.e. without rotation of gears 23 and 24 with respect to each other and of the planetary gears 25, 26, 28 and 29 with respect to the cage 22). With such torque loads on gears 23 and 24, rotation applied by worm 32 to the cage 22 will cause the gears 23 and 24 to rotate together and with the cage, all three through the same angle. If the tensions in the threads 11 and 12 tend to impose on gears 23 and 24 torques related otherwise than as to 1 to 2, then differential action will occur until those torques are so related. That is to say, the torque loads on gears 23 and 24 must be in the ratio of 1 to 2 in order to avoid differential action, and, subject to the effect of friction in the differential 21, that differential acts to preserve this relation between the torques on gears 23 and 24.

In the embodiment of FIG. 3 instead, equal torque loads can be sustained on gears 24 and 68 without differential action in differential 61, and with such equal torque loads the torque on shaft 60 (and hence on beam 3) will be one half that on shaft 19 (and on beam 4). When the cage 62 is rotated by worm 32, equal output rotations to gears 24 and 68 would produce rotation of shaft 60 (i.e. of beam 3) twice as great as the rotation of shaft 19 (i.e. of beam 4), destroying the equality of the torque loads on gears 24 and 68. Hence in the embodiment of FIG. 3, in contrast to that of FIG. 1, differential action is the normal and not merely the exceptional state of affairs, the input rotation being stepped up as to shaft 19 and stepped down as to shaft 69, preserving equal torques on gears 24 and 68, and thereby preserving a torque on shaft 60 one half that on shaft 19. In this respect the operation of the embodiment of FIG. 5 is essentially the same as that of FIG. 3, as is also that of FIG. 7 as regards the differential gear train 106 thereof.

It will thus be seen that the invention provides a warp let-off motion for a loom having a plurality of warp beams, and a controllably rotatable shaft such as that of the worm 32 of FIGS. 1 and 3. The motion further comprises a transmission coupling the warp beams together. This transmission includes as part thereof a differential gear train having three driving points, the differential being connected at two of its driving points in series in that transmission and the controllably rotatable shaft being connected to the third driving point of the differential, the transmission having a non-unity drive ratio such that for zero rotation of the third driving point rotation of one of the warp beams through a first angle effects rotation of the other warp beam through a different angle. In the embodiment of FIG. 1, for example, the transmission may be identified as extending from beam 3 via gear 14, pinion 16 and shaft 15 to gear 23 as one of the driving points of differential gear train 21, through differential gear train 21 to gear 24 thereof (a second driving point of that differential) and thence via shaft 19, pinion 18 and gear 17 to the second warp' beam 4. The controllable motion of shaft 33 is applied via worm 32 and worm wheel 31 to the cage or housing 22 which constitutes the third driving point of that differential. The transmission so extending from beam 3 to beam 4 has a non-unity drive ratio, in that if cage 22 is held stationary, rotation of beam 3 through one angle will result in rotation of beam 4 through one half that angle. In the embodiment of FIGS. 3 and 5 the transmission may be similarly identified, the essential difference being that in these embodiments the non-unity drive ratio of the transmission is determined by elements of the transmission outside the differential.

While the invention has been described hereinabove in terms of a number of presently preferred embodiments thereof, the invention itself is not limited thereto but rather comprehends all modifications on and departures from those embodiments properly falling within the spirit and scope of the appended claims.

I claim:

1. Warp let-off apparatus. for a loom, said apparatus comprising at least two warp beams, a differential gear train having three driving points, separate linkages coupling each of said beams to a separate one of said driving points, and means to apply a rotation to the third of said driving points, the transmission drive ratio between said beams via said differential gear train being non-unity.

2. Warp let-off apparatus according to claim 1 wherein said drive ratio is substantially equal to the ratio of the widths of said beams.

3. Warp let-off apparatus according to claim 1 wherein said differential gear train exhibits a non-unity drive ratio between said separate ones of said driving points.

4. Warp let-off apparatus according to claim 1 wherein at least one of said linkages possesses a non-unity drive ratio.

5. Warp let-off apparatus according to claim 1 wherein one of said linkages includes a second differential gear train having three driving points, two driving points of said second differential gear train being connected in series in said one linkage, said apparatus including a further warp beam coupled to the third drive point of said second differential gear train.

6. Warp let-off apparatus for a loom, said apparatus comprising at least two warp beams, a controllably rotatable shaft, a transmission coupling said beams to each other,

13 14 said transmission including a differential gear train hav- 1,749,131 3/1930 Davis 139-108 ing three driving points, two of said driving points being 1,827,712 10/ 1931 Davis 139-103 connected in series in said transmission between said 3,157,207 11/ 1964 Parrwaller 139--97 beams, and means coupling said shaft to the third driving FOREIGN PATENTS point of said differential gear train, said transmission hav- 5 ing a non-unity drive ratio whereby for Zero rotation of said third driving point rotation of one of said beams 1,161,733 3/1958 France. 1,440,960 4/1966 France.

through a first angle effects rotation of the other of said 1,008,773 11/1965 Great Britainbcams thmgh dfierem angle JAMES KEE CHI, Primary Examiner.

References Cited 10 CL R UNITED STATES PATENTS 139-403 69,320 10/1867 Cottrell et al 139-101 775,336 11/1904 Meats 139-101 

